Optical Waveguide Interferometer for Ultrasonic Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical detection systems for ultrasonic waves in materials suffer from low sensitivity due to diffusely reflecting or scattering surfaces, leading to aberrated and mismatched wavefronts, resulting in weak and imprecise signals.
Innovation Solution
An optical waveguide interferometer with a reference arm and measurement arm, adjusted by a controller to maintain a constant optical path length, using a probe segment to sense ultrasonic waves induced by an excitation source, and a second optical detector to refine the reference arm's path length, ensuring accurate signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser probe beam is directed onto a diffusely reflecting surface to detect ultrasonic waves, then the surface vibration can be detected, but the reflected beam becomes highly aberrated and mismatched with the reference beam, resulting in weak and imprecise signals
Solution Approach 1:
The patent introduces a refractive index matching fluid as an intermediary substance between the optical probe and the test surface. This fluid acts as a mediator that optically couples the probe to the surface, eliminating air gaps and reducing refractive index mismatches that cause aberrations. The fluid fills the interface between the probe lens and the diffusely reflecting surface, creating a controlled optical pathway that maintains beam quality while allowing detection of surface vibrations.
2Reliability
If the optical path length between the probe beam and the surface fluctuates, then the detection system becomes sensitive to path length changes, but maintaining a constant path length is difficult to achieve
Solution Approach 1:
The patent implements a feedback control mechanism where a portion of the reference beam is directed to a reference surface at a known distance. The optical path length to this reference surface is measured and used to generate a feedback signal. This feedback is then fed to a controller that adjusts the position of the reference arm to maintain a constant optical path length difference between the measurement and reference arms, ensuring stable interferometric detection despite environmental variations.
3Measurement precision
If a reference beam is directed onto the same diffusely reflecting surface as the probe beam, then the interferometric detection can be performed, but the mismatched wavefronts from the aberrated reflected beam reduce the quality of the interference pattern
Solution Approach 1:
The refractive index matching fluid serves as an intermediary that improves wavefront matching for both the probe and reference beams. By filling the optical pathway between the probe/reference sources and the diffusely reflecting surface, the fluid creates a controlled refractive environment that minimizes aberrations and maintains more consistent wavefront shapes, enabling better interference pattern formation.
Solution Approach 2:
The patent replaces traditional mechanical alignment methods with an optical coupling approach using refractive index matching. Instead of mechanically adjusting the probe and reference beam paths to achieve alignment, the system uses the optical properties of the matching fluid to automatically optimize the optical coupling between the beams and the surface, simplifying the alignment process and improving wavefront matching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the accuracy of ultrasonic wave detection by maintaining a stable optical path length, reducing the impact of surface aberrations and fluctuations, resulting in more precise measurements of material properties like thickness and composition.
Implementation Method 1
mixing the reflected probe beam with a stable reference beam and measuring the amplitude and frequency or phase of the photodetector output intensity fluctuations
Implementation Method 2
When the surface vibrates it imparts a phase shift onto the reflected beam. This phase shift is detected with a photodetector
Implementation Method 3
The ultrasonic waves are typically generated with a piezoelectric transducer
Implementation Method 4
an optical waveguide interferometer with a reference arm and measurement arm, adjusted by a controller to maintain a constant optical path length
Data Source
AI summary
A sensing apparatus includes an excitation source configured to induce waves in a target, and an optical waveguide interferometer configured to sense the induced waves in the target. The optical waveguide interferometer includes a plurality of optical couplers and interconnecting optical fibers arranged to define a reference arm, a measurement arm, and a probe segment coupled to the reference arm and the measurement arm and having a probe segment end to be positioned adjacent the target. An optical path length adjustor is coupled to the reference arm. A controller cooperates with the path length adjustor and is configured to adjust an optical path length of the reference arm to maintain a constant relationship with respect to an optical path length of the measurement arm.